Patent Literature 1 discloses a device that detects the values on capacitors distributed in a matrix manner, e.g. a capacitance detecting device that detects a distribution of the electrostatic capacitances of capacitors arranged in rows and columns demarcated by M drive lines and L sense lines. This capacitance detecting device detects the touch of a finger or a pen by detecting a change in capacitance, as a finger or a pen touching an area on the touch panel causes a change in capacitance of a capacitor located in the area.
FIG. 16 is a schematic view showing a configuration of a conventional touch panel system 91. FIG. 17 is a diagram for explaining a method for driving the touch panel system 91. The touch panel system 91 includes a touch panel 92. The touch panel 92 has drive lines DL1 to DL4, sense lines SL1 to SL4, and capacitors C11 to C44 disposed in locations at intersections between the drive lines DL1 to DL4 and the sense lines SL1 to SL4.
The touch panel system 91 is provided with a drive section 94. The drive section 94 drives the drive lines DL1 to DL4 on the basis of a 4×4 code sequence shown in Exp. 3 of FIG. 17. The drive section 94 applies a voltage Vdrive when an element of the code matrix is “1”, and applies a zero voltage in the case of an element “0”.
The touch panel system 91 has four amplifiers 98 disposed in locations corresponding to the sense lines SL1 to SL4, respectively. The amplifiers 98 receive and amplify linear sums Y1, Y2, Y3, and Y4 of electrostatic capacitances along with the sense lines driven by the drive section 94, respectively.
For example, in the first round of driving of the four rounds of driving based on the 4×4 code sequence, the drive section 94 applies the voltage Vdrive to the drive line DL1 and applies a zero voltage to the remaining drive lines DL2 to DL4. Then, for example, the measured value Y1 from the sense line SL3 corresponding to the capacitor C31 as indicated by Exp. 1 of FIG. 17 is outputted from the amplifier 98.
Then, in the second round of driving, the drive section 94 applies the voltage Vdrive to the drive line DL2 and applies a zero voltage to the remaining drive lines DL1, DL3, and DL4. Then, the measured value Y2 from the sense line SL3 corresponding to the capacitor C32 as indicated by Exp. 2 of FIG. 17 is outputted from the amplifier 98.
Next, in the third round of driving, the drive section 94 applies the voltage Vdrive to the drive line DL3 and applies a zero voltage to the remaining drive lines. After that, in the fourth round of driving, the drive section 94 applies the voltage Vdrive to the drive line DL4 and applies a zero voltage to the remaining drive lines.
Then, as indicated by Exp. 3 and Exp. 4 of FIG. 17, the measured values Y1, Y2, Y3, and Y4 per se are associated with the electrostatic capacitances C1, C2, C3, and C4, respectively. In Exp. 3 and Exp. 4 of FIG. 17, the measured values Y1, Y2, Y3, and Y4 are described with the omission of a coefficient (−Vdrive/Cint) for simplicity of notation.